Left ventricular (LV) remodeling is a common adverse event following myocardial ischemia and reperfusion (I/R) and can result in LV failure and mortality. While this process is multifactorial, this laboratory and others have established that the induction of a family of extracellular matrix (ECM) proteolytic enzymes, the matrix metalloproteinases (MMPs) contribute to adverse LV remodeling post-I/R. During the past performance period, we established that a unique membrane specific MMP, the membrane type-1 MMP (MT1-MMP), is increased following I/R. Since MT1-MMP possesses multiple biological actions and is robustly expressed on the myocyte sarcolemma, then it follows that MT1-MMP may play an important role in I/R injury. The release of bioactive signaling molecules such as endothelin (ET) occurs during and following I/R and was the focus of our studies during the last project performance period. Specifically, it was demonstrated that a surge of ET occurs within the myocardial ECM with I/R and was associated with an induction of a unique cassette of protein kinase C (PKC) isoforms. The central hypothesis of this ongoing research effort is that induction of a specific MMP type (MT1-MMP) occurs with I/R and that increased ET release into the myocardial ECM causes a PKC isoform dependent amplification of MT1-MMP. Using cell based studies, murine constructs, and a porcine I/R model, this hypothesis will be tested by accomplishing the following specific aims: (1) Demonstrate in an isolated LV myocyte system of I/R, that intracellular trafficking of MT1-MMP occurs which is regulated in part by ET receptor stimulation and activation of specific PKC isoforms. (2) Demonstrate in the intact murine system that ET regulates MT1-MMP induction with I/R and is a determinant of LV contractility. (3) Demonstrate increased regional interstitial ET causes MT1-MMP activation and LV dysfunction in a porcine I/R model, which is time dependent. The outcome from these integrated studies will identify a unique extracellular mechanism by which ET can contribute to regional LV dysfunction in the context of I/R and identify potential therapeutic targets to ameliorate this process. PUBLIC HEALTH RELEVANCE: One of the most common causes of death and disability in this country is from a heart attack;damage to the heart muscle. Following a heart attack, it is now clear that enzymes are made that continue to chew away at the heart muscle and eventually cause the heart to change shape and fail. This study will identify how to control a critical enzyme which causes the heart to fail following a heart attack and thereby develop new tests and treatments for patients after a heart attack.